CHAPTER XXXIII.

PLANTS OF LONG AGO

When we were on the moors we noticed that we may sometimes find plants being actually turned to stone under our eyes (~see~ p. 156). These are plants which are living at the present time, but this same thing has also happened to plants which lived long ago, and which otherwise we could not see and study, because they are all dead. In those cases in which they did not decompose in the ordinary way after death, but were turned to stone, we are sometimes able to find out almost as much about them as we can about the plants living to-day.

You must have seen in museums, or even found for yourself in stones, the remains of leaves and stems of plants which, too, are turned to stone, but which yet show the shape and form of the plant with great beauty. If you go to the north of England, where there are many coal-mines, you will have a good chance of finding pieces of stone which have been thrown out from the mines as refuse, and which have in them or on them most beautiful leaves of ferns and other plants. We know from geologists that these rocks are very old indeed, older than the valleys and downs of the south of England, yet we can see to-day what the plants which lived then looked like, because they have been turned into stone and kept for us in the rocks till the miners dig them out when digging the coal.

But what is coal itself? You know that it is not at all like an ordinary rock, for it burns as well as wood, and has been found to be largely made of carbon. Even directly on top of the coal, and sometimes actually in the coal seams, we find plants preserved, and geologists and botanists have combined to prove that coal is really entirely composed of the crushed remains of ancient plants.

You will remember that we found that many of the plants in the peat bogs did not get decomposed entirely because of the preservative peaty acids present in the water and soil. Something of the same kind happened to the plants of the old forests which now form our coal. As they died they did not entirely decompose, but got pressed tightly together, all their living juices being squeezed away till little but the carbon in them remained. These masses of plants gradually sank beneath the sea, were covered by sandstones and limestones, and were preserved between the beds of rock, forming masses nearly as firm as the rocks themselves. These old plants, which to-day act as our fuel, are really “as old as the hills,” for they were growing in the country before the hills were made.

As well as the many plants which were preserved in this way, and in which we can now see little but masses of carbon, there were others which were preserved in stone, sometimes pressed between the layers of stone as you press a flower between sheets of blotting-paper, in other cases turned directly into stone without crushing, so that they show their complete form, cell by cell. It is from these stone plants that we learn what the plants of the coal were like. Sometimes we find great trunks of trees standing petrified together in the positions in which they were growing, with their roots twining round one another, and entering the muddy soil on which they lived. Sometimes such tree-stumps stand up through the coal-beds and rocks which must have been deposited all round them (~see~ fig. 153). We find also leaves and stems, cones and seeds, in the stones, till we can build up completely the form and life history of several of the plants which were then living. But in all the wealth of material which has been found, no flowers have ever been discovered. The seeds seem to have belonged to plants of the pine-tree family, so that these old forests were without any of the plants which are to-day the most important family of all, that is, the flowering plants. They lived so long ago that flowers had not come into existence by that time.

Another strange thing about these forests is, that although there were great trees in them, they were not like those of our present forests. To-day our trees are chiefly flowering plants, such as oaks, limes, and beeches; but the giants of these ancient forests were club-mosses and horsetails, plants belonging to the fern tribe. Their descendants, the club-mosses and horsetails growing now, have degenerated, and are humble plants not more than a few feet high at the most, and always of little real importance in the landscape.

The true ferns then living seem to have been more like those of the present, though perhaps a little larger and more important. In the family of ferns then living were some with strange histories, and among the ferns which you may find in the stones some leaves may have belonged to a plant which was truly a “missing link” in the history of plants, and helps us to see the relationship between ferns and pines.

Many and strange are the tales the fossil plants can tell us of the life in the forests when the coal was made, and just as, in the moors, only those moss-plants which were turned to stone will still be there after centuries have gone by, so it was in the old coal-forests that only the plants which were turned to stone remain to tell us their story to-day. For this reason our knowledge of the forests of long ago is not complete; but even now it is enough to tell us something of the life of the plants which were then doing the food-building work of the world. Though the individual plants were so different, the “associations” were in a general way the same as those now living. Great trees reared their heads into the air, and below them, or climbing round and over them, the smaller plants found place long ago as they do to-day.